Do we need to keep the hood up to cool the engine after a long drive?

This is a discussion on Do we need to keep the hood up to cool the engine after a long drive? within Technical Stuff, part of the Under the Hood category; Like all others here i too agree that modern cars have no reason what so ever to have their hoods ...

Re: Do we need to keep the hood up to cool the engine after a long drive?

Like all others here i too agree that modern cars have no reason what so ever to have their hoods popped after long drives.
However never mistake that just being a modern car won't help. If its ill maintained these problems will crop up in future.
Am on a trip to Panchgani (Maharashtra) as i write this and when i arrives here yesterday afternoon the entire Pasarni ghat before Panchgani was packed with bumper to bumper traffic. Almost the entire ghat section of 7-8 kms was covered crawling in 1st and 2nd gears. And from what i noticed the crawling traffic and driving in 1st and 2nd gears had a toll on my 3 yr old "modern" Swift as well. My temp needle had shot a few centimeters above the usual half way mark.
Also saw a good number of cars halted by the ghat sides and had their hoods opened for cooling. Rest assured most of them i saw were M800s/Santros/Altos first gen mostly. Even saw a first gen Laura opened up for cooling. Surprisingly even a new Celerio!
Surprisingly the decade old State Transport buses managed just fine in the crawling traffic with not a single bus halting to cool off.

However i would like to mention that heat has somewhat cracked and broken off the black contraption holding my car's battery. Sorry don't know what it's called

Re: Do we need to keep the hood up to cool the engine after a long drive?

Quote:

Originally Posted by sriramr9

I have had first hand experience in watching this same technique followed in Matador fitted ambassadors which are cooled with Regular water.

After several hours of drive in mid day in ghats, the driver who is pretty aware of the spots to get water, will stop by, without turning off the engine, will pop the hood and grab the required qty of water required from the known pit stop and first pour it carefully over the entire length of the radiator to kind of give the super heated radiator a respite and after a couple of minutes of breather would slowly open the radiator cap ensuring the steam does not cause it fly upwards, once opened. he will pull the throttle cable directly and cause the engine to revv and simultaneously fill up the radiator with fresh cool water, the more he revvs the more the radiator will gulp up without water over flowing. This was carried out till the radiator was full and was cooled completely and stopped steaming.

Upon questioning he says this is the best way to cool a over heated engine and is being followed for decades, of course after the 10 minute instant cooling ordeal, the engine did feel better while accelerating (gut feeling), the radiator steamed less.

Can only imagine all that nowadays.

+1 to that. The same technique mentioned above was used by our driver with our Old Amby. He made sure whenever we went for long drives, he had an empty Gallon or a bucket in the car's boot to get water in case if we had to stop for cooling the engine.

Re: Do we need to keep the hood up to cool the engine after a long drive?

From day one, I follow the practice of religiously opening the engine hood during my numerous medium and long distance travels during breaks. Although, the modern engines are capable of withstanding a good amount of continuous running of the engine without increase in its operating temperature, it would do no harm to let the heat dissipate more faster through the hood opening rather than just through the vents or openings in the vehicle. This would also help to increase the life of other elements like tubings, plastics etc which are sensitive to heat by faster removal of hot air from the engine bay. Moreover during driving the air carries away the heat whereas when the vehicle is stationary, the heat dissipation is slower from the confined space.

Offcourse care to be take to ensure no liquid / objects falls in the engine bay and no childrens venture close by when the hood is open.

Re: Do we need to keep the hood up to cool the engine after a long drive?

We have a 1988 Amby and we have never had to do this. It was fitted with Isuzu engine with ac soon after it was bought and I think one time the coolant leaked out and there was green color coolant on the floor. Other than that time I dont remember us opening the bonnet to cool of the engine. This car has done many long drives including from Delhi to Chennai by road in about 3 days.

On a another note I live in the middle east these days and if opening the bonnet was the norm then everyone here has to be opening the bonnet after a drive .

Re: Do we need to keep the hood up to cool the engine after a long drive?

Quote:

Originally Posted by Gansan

This is why after every drive before shutting down the engine I will :

1) Listen for the fan motor. If it is running I will wait for it to go off and then shut down.

Quote:

Originally Posted by Desmosedici

If the fan is on, i wait till it switches off and only then kill the engine.

What came first - the chicken or the egg ?

The fan is coming on to keep the engine cool as, when idling, there is no flow of air. You sir, on the other hand, are keeping the engine idling because the fan is on.

Quote:

Originally Posted by King_pin09

Sir, why do you want to cool down the engine, at the first place unless it crosses the limit on the temp guage? Your car is designed to run at an optimal temperature so even if you cool it down for a while, it attains this temperature once again within seconds of restarting.

The onboard computer on your car is already aware of the engine temperatures and maintains it by its own way. Your car is designed to run as such, without your additional efforts each time by opening the bonnet.

Awesome post!

Quote:

Originally Posted by VeyronSuperSprt

The opposite is true - when starting off from a hill station and going down hill the engine does not generate enough heat

Any modern engine will reach its optimal operating temperature within ~1 km of driving. Even if going downhill.

Quote:

Originally Posted by bhandary

it would do no harm to let the heat dissipate more faster through the hood opening rather than just through the vents or openings in the vehicle. This would also help to increase the life of other elements like tubings, plastics etc which are sensitive to heat by faster removal of hot air from the engine bay.

All of the tubings & plastics lasted 2 lakh kms in my Esteem (and perhaps more with the 2nd owner) without opening the bonnet. How much more do you want to extend their life?

Re: Do we need to keep the hood up to cool the engine after a long drive?

Quote:

Originally Posted by bhandary

it would do no harm to let the heat dissipate more faster through the hood opening rather than just through the vents or openings in the vehicle. This would also help to increase the life of other elements like tubings, plastics etc which are sensitive to heat by faster removal of hot air from the engine bay..

Sir, many people fail to appreciate that each part used in the car comes with specifications that are set out based on the respective functions such part is supposed to render. Thus the material used for casting all tubings and plastics in the engine bay are pre determined to withstand the heating and cooling processes that takes place in the engine bay.

Besides, this alternative heating and gradual cooling of the elements cause them to undergo a time driven process of micro structure reorganisation called “annealing”, thereby enhancing their life span. Therefore, these plastics/ rubber or other materials last their full life when they are subject to the conditions under which they are supposed to be in.

Steep/ assisted / forced cooling by way of opening the bonnet will not bring any benefit, but instead shall partially induce a phenomenon called “tempering” which will cause them become hard and brittle, and eventually cause cracks and fail prematurely.

Re: Do we need to keep the hood up to cool the engine after a long drive?

A quite the opposite practice, off-topic here but funnily useful enough to mention. We used to light up a fire under the diesel tank of our Mahindra MM550 (Army 4x4) to de-freeze the fuel while operating between Drass and Gumri in the cooler seasons! The first time it was done, I was aghast but thereafter it became an acceptable practice!

Re: Do we need to keep the hood up to cool the engine after a long drive?

Quote:

Originally Posted by GTO

What came first - the chicken or the egg ?

The fan is coming on to keep the engine cool as, when idling, there is no flow of air. You sir, on the other hand, are keeping the engine idling because the fan is on.

Who cares as long as it tastes good

The fans job is to keep the engine cool, agreed. In my Ecoboost, even during / after a long highway drive where there is a continuous airflow to keep the engine at optimum temp, the fan is always on. I have observed this several times. The fan would stay on for some time even after switching off the car.

Once it ran for a full minute post switching off and that running would obviously be powered by the battery. Call me paranoid (have had many instances due to battery woes) but i would prefer that everything shuts down before i kill the engine and lock the car.

Re: Do we need to keep the hood up to cool the engine after a long drive?

I remember my Dad doing this to our family cars - a Toyota Corona, Ambassadors, Standard Heralds and of course the ubiquitous FIAT/Premier Padmini when I was a kid back in the 1970s.

Fast forward 40 years - I never raise the hood to let the engine cool. The cooling system takes care of that. The only time I'd raise the hood is if the coolant temp shot over the normal mark which it never has regardless of where I am driving - hills/ghats, stop and go traffic, open roads at sustained highway speeds of >120 kmph all with the AC on, a boot full of luggage and 4 passengers.

Keep your car's cooling system in good shape, that's all that is required - change the coolant at recommended intervals or even earlier and do not add tap or well water except in an emergency. If tap/well water is added in extenuating circumstances please drain the radiator and refill with manufacturer recommended fluid. You don't want hard water deposits clogging the radiator or passageways in the block.

I changed my low mileage car's premixed coolant at the 5 year mark even though the manufacturer recommends 10 years/160,000 kms for the factory filled coolant.

I also keep the engine running if the radiator cum AC fan goes on. This is a 10A fan but it goes off when I cut the ignition. With the Palio the fan remains on even when the engine is cut, running off the battery in the process. So, with this car there's a reason for me to keep the engine running till the fan goes off automatically. I prefer it not drain the 5 year old battery which could be up for replacement soon.

Re: Do we need to keep the hood up to cool the engine after a long drive?

Quote:

Originally Posted by Gansan

This is why after every drive before shutting down the engine I will :
1) Listen for the fan motor. If it is running I will wait for it to go off and then shut down.
2) If the fan motor is not audible, I will idle the engine for a minute or so to see if it switches on, and then shut the engine down.
After shutting down also I will once again move the key to ignition on position and check if the fan motor comes on.

I think the first rule is OK, I do the same, i.e. let the engine run till the fan switches off.
In my F10D Alto, the fan comes on at ~98 C & stays on till ~88 C ( OBD data ).
I keep the engine running because that's the only way the water pump's on, & the coolant cooled by the radiator + fan combo can get to the coolant temperature sensor ( which is on the block ).
If you continue to run the engine after the fan turns off you would just be getting the temperature to rise again.
In any case, the fan lowers the coolant temperature to ~88 C only, even with Chennai temperatures, there's a long way to go to cool down to the ambient temperature.
In general, I've never seen the fan turn on ( rigged an LED to let me know when the fan turns on ) when the car's running & there's airflow through the radiator, even at low speeds ( of course if the A/C's on, the fan's always on ).

Quote:

Originally Posted by dhanushs

Each car's ECU has its own set of rules for switching off the fan.

I guess so, but I never understood the logic of turning the fan on when the engine's off.
I mean, the coolant temperature sensor is usually close to the block, & if the engine's off, so is the water pump.
So turning the fan on with the water pump off appears illogical to me considering the temperature's sensed somewhere else.
I understand that in old cars, radiators were placed slightly higher than the block to allow heated coolant to sort of rise up & flow to the radiator, but I don't think modern cooling systems still employ this practise.

I guess there are still a lot of myths & superstitions around cars & how to operate & maintain them - maybe the engineers should add this topic to the myth-busting thread - (Automotive misconceptions demystified)
.

Re: Do we need to keep the hood up to cool the engine after a long drive?

It's not only Fiat engines that run after the engine is switched off. It happens to Ford engines also, though occasionally. As far as i know, my Fiesta's engine stays on for a minute after switching off mostly after driving amid thick traffic in summer.

The only time it remained on for around 4 to 5 minutes after switching off was after reaching YMCA, Ooty after the tortuous 36-hairpin route and the narrow, congested roads at Ooty. I was a bit alarmed and stationed my son near the car till it switched off, while I was completing entry formalities at the reception.

I felt relieved when he told it that it switched off. And I had not bothered to open the hood.

Re: Do we need to keep the hood up to cool the engine after a long drive?

This is one of the important topics, which concerns all of us; since this thread has been created and members are participating why not GTO provides a discourse on engine temperature management.

- I doubt if oil cooled engines are present in modern day cars atleast not on this side of 30 Lac or so; most of us find our cars water based coolant systems. The only thing that worries me is mixing of coolant, which is even done at the authorized service stations (I have seen this being practiced at Tatas as well as Hyundai) as I remember the same service station using a different brand during previous service. Fiat for that matter, which is with me since 2013 has always been topped up with same coolant. The volume is not much, I would say about 100 ml or so. I have checked with SA and have been given the answer that it doesn't matter. The forum's view is otherwise.

- Ford Escort, which was my first acquisition in 1997 uses a different coolant (which is of pink color and not the standard green color), even Fiat uses pink color coolant. What is the difference? Fiat advised change of coolant every 2 years while Ford every 5 years - both are pink in color. Tata - never bothered even by Concorde Motors and Hyundai tries to suggest at every alternate service. I know every manufacturer has different specification and advise on coolant, yet there should be a good thumb rule for such things; may be some information on brands of coolant too?

- I have only faced coolant leakage issues in my Indica, which made me finally letting her go. Neither my FNG nor Concorde Motors were able to fix it; the answer given to me was "apki gaadi gas banati hai" I have no idea what is that. Got it fixed 3 times in a year and finally decided to give it in exchange of Punto

As far as long distance travel are concerned, I have done several and have never seen any issue / need to open the hood. As a regular practice, I do open the hood once in 15 days and check fluids including the engine oil, remove the dust from engine bay with a dry cloth and have always seen my cars smiling back at me.